C-reactive protein (CRP) is a marker of low-grade inflammation, which appears to be a strong predictor of future disease. Adiposity and cardiorespiratory fitness have both been associated with CRP in every age group, but studies disagree on which factor is more important to prevent lifestyle-related diseases. The purpose of this study was to examine the relative impact of adiposity and cardiorespiratory fitness (CRF) on CRP in eighteen year-old teenagers in high school. A secondary purpose was to examine which factor, adiposity or CRF, would be more important in association with CRP. Height, weight and waist circumference of 245 teenagers were assessed and body mass index (BMI = kg/m2) calculated. DXA (dual energy X-ray absorptiometry) was used to measure body composition; bone mass, fat mass and fat-free mass. CFR was assessed via maximal oxygen uptake (VO2max) test on a treadmill and a blood test was taken to evaluate their CRP for disease risk later in life.CRP was correlated to all fatness measures (r = 0.24-0.33; all with P < 0.001) and fitness (r = -0.29, P < 0.001) where android fat and percent fat were the strongest predictors of CRP (r = 0.31-0.33, P < 0.001). The teenagers who were classified in the low fitness/high fatness group, when percent fat was used to group participants based on fatness, had significantly higher CRP, than both groups with high fitness (high fitness/low fatness, P < 0.001; high fitness/high fatness, P = 0.004). The difference between high fitness/high fatness and high fitness/low fatness groups was also significant (P = 0.021). The teenagers in the high fitness/low fatness group had significantly lower CRP (low fitness/low fatness, P = 0.017; high fitness/high fatness, P = 0.006; low fitness/high fatness, P < 0.001) when BMI was used to group participants based on fatness. The main result is that adiposity and CRF are both associated with CRP but adiposity had a stronger relation than CRF among teenagers although the latter also appears to be a relatively strong predictor. Mixture of both (low fat, high CRF) is probably most effective in reducing the possibility of diseases later in life.